WEIGHT-LOSS IN RATS PRODUCED BY RUNNING - EFFECTS OF PRIOR EXPERIENCEAND INDIVIDUAL HOUSING

To investigate factors affecting activity-based anorexia (ABA) or acti vity-stress (AS), rats were given 2-hr access to a running wheel immed iately prior to their daily 1.5-hr food access during the light cycle. This produced a reduction in food intake, a steady increase in runnin g, and a large drop in body weight with a prolonged delay before weigh t recovery began. Experiment 1 found that these effects were reduced i n rats with prior experience of eating at this time of day. In contras t, prior experience of running in the wheel when on ad lib food enhanc ed these effects in Experiment 2, where a subsequent change for half t he subjects to individual housing produced a further decrease in body weight. The latter factor was investigated from the outset of Experime nt 3 and again individually housed rats showed greater weight loss tha n did group-housed rats. This experiment also found that in rats of th e same age a low initial body weight predicts greater vulnerability to ABA. It was concluded that ABA results from activity-induced reductio n of feeding, which prolongs adaptation to a new feeding schedule and is accentuated by social isolation.